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Updates MESSENGER Mission News
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JHU APL - MESSENGER:
MESSENGER Mission News
November 14, 2013
http://messenger.jhuapl.edu/
MESSENGER Detects Comets ISON and Encke, Prepares for Closer Encounters
NASA's Mercury-orbiting MESSENGER spacecraft has captured images of two comets -- 2P/Encke and C/2012 S1 (ISON) -- setting the stage for observations later this month when both comets will be substantially brighter and much closer to Mercury and the Sun.
ISON was discovered in September 2012 by amateur Russian astronomers, who observed with a 16-inch telescope that is part of the International Scientific Optical Network (ISON), after which the comet was named. On November 28, ISON will fly within 700,000 miles (1.2 million kilometers) of the Sun's photosphere, at which time it is expected either to flare brilliantly or disintegrate.
As part of an ISON observation campaign involving ground- and space-based NASA observatories, as well as many other observatories around the world, MESSENGER has been poised for several weeks to collect observations of ISON. From November 9 through November 11, the probe's Mercury Dual Instrument System (MDIS) captured its first images of the comet.
"We are thrilled to see that we've detected ISON," said Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER's role in the ISON observation campaign. "The comet hasn't brightened as quickly as originally predicted, so we wondered how well we would do. Seeing it this early bodes well for our later observations."
A few days earlier, from November 6 through November 8, MESSENGER's imagers picked up its first snapshots of Encke. Unlike ISON, Encke has been known for quite a while. It was discovered in 1786 and recognized as a periodic comet in 1819. Its orbital period is 3.3 years -- the shortest period of any known comet -- and November 21 will mark its 62nd recorded perihelion.
"Encke has been on our radar for a long time because we've realized that it would be crossing MESSENGER's path in mid-November of this year," Vervack explained. "And not only crossing it, but coming very close to Mercury." These early images of both comets are little more than a few pixels across, Vervack said, but he expects improved images next week when the comets make their closest approaches to MESSENGER and Mercury.
On November 18, just a few days shy of its perihelion on November 21, Encke will travel within 2.3 million miles (3.7 million kilometers) of Mercury. According to the Minor Planet Center, if Encke came this close to Earth, it would rank as the third closest known approach of a comet to our planet. On November 19, ISON will pass within 22.5 million miles (36.2 million kilometers) of Mercury while at a distance of 44 million (71 million kilometers) from the Sun.
"By next week, we expect Encke to brighten by approximately a factor of 200 as seen from Mercury, and ISON by a factor of 15 or more," Vervack said. "So we have high hopes for better images and data." Three of MESSENGER's instruments -- MDIS, the Mercury Atmospheric and Surface Composition Spectrometer, and the X-Ray Spectrometer -- will be trained on the two comets and will collect as many observations as payload operational constraints will allow.
There are complicating issues that could impact the volume of data the team gathers, Vervack explained. "Closest approach occurs during what we call a 'hot season,'" he said. "So, for the health of the spacecraft, portions of each orbit must be spent in a thermally safe mode, which precludes gathering data over the entire orbit."
The critical observations also happen during a low-downlink period for MESSENGER. "We can't fill up the spacecraft recorder with comet data because doing so could cause a backlog that impacts our primary mission of collecting observations from Mercury," he said.
But the team is optimistic that all will go as planned, he said. "We just need the comets to hold up their end of the bargain."
{...}
JHU APL - MESSENGER: MESSENGER's First Images of Comets Encke and ISON
Universe Today: Comets Encke and ISON Spotted from Mercury
MESSENGER Mission News
November 14, 2013
http://messenger.jhuapl.edu/
MESSENGER Detects Comets ISON and Encke, Prepares for Closer Encounters
NASA's Mercury-orbiting MESSENGER spacecraft has captured images of two comets -- 2P/Encke and C/2012 S1 (ISON) -- setting the stage for observations later this month when both comets will be substantially brighter and much closer to Mercury and the Sun.
ISON was discovered in September 2012 by amateur Russian astronomers, who observed with a 16-inch telescope that is part of the International Scientific Optical Network (ISON), after which the comet was named. On November 28, ISON will fly within 700,000 miles (1.2 million kilometers) of the Sun's photosphere, at which time it is expected either to flare brilliantly or disintegrate.
As part of an ISON observation campaign involving ground- and space-based NASA observatories, as well as many other observatories around the world, MESSENGER has been poised for several weeks to collect observations of ISON. From November 9 through November 11, the probe's Mercury Dual Instrument System (MDIS) captured its first images of the comet.
"We are thrilled to see that we've detected ISON," said Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER's role in the ISON observation campaign. "The comet hasn't brightened as quickly as originally predicted, so we wondered how well we would do. Seeing it this early bodes well for our later observations."
A few days earlier, from November 6 through November 8, MESSENGER's imagers picked up its first snapshots of Encke. Unlike ISON, Encke has been known for quite a while. It was discovered in 1786 and recognized as a periodic comet in 1819. Its orbital period is 3.3 years -- the shortest period of any known comet -- and November 21 will mark its 62nd recorded perihelion.
"Encke has been on our radar for a long time because we've realized that it would be crossing MESSENGER's path in mid-November of this year," Vervack explained. "And not only crossing it, but coming very close to Mercury." These early images of both comets are little more than a few pixels across, Vervack said, but he expects improved images next week when the comets make their closest approaches to MESSENGER and Mercury.
On November 18, just a few days shy of its perihelion on November 21, Encke will travel within 2.3 million miles (3.7 million kilometers) of Mercury. According to the Minor Planet Center, if Encke came this close to Earth, it would rank as the third closest known approach of a comet to our planet. On November 19, ISON will pass within 22.5 million miles (36.2 million kilometers) of Mercury while at a distance of 44 million (71 million kilometers) from the Sun.
"By next week, we expect Encke to brighten by approximately a factor of 200 as seen from Mercury, and ISON by a factor of 15 or more," Vervack said. "So we have high hopes for better images and data." Three of MESSENGER's instruments -- MDIS, the Mercury Atmospheric and Surface Composition Spectrometer, and the X-Ray Spectrometer -- will be trained on the two comets and will collect as many observations as payload operational constraints will allow.
There are complicating issues that could impact the volume of data the team gathers, Vervack explained. "Closest approach occurs during what we call a 'hot season,'" he said. "So, for the health of the spacecraft, portions of each orbit must be spent in a thermally safe mode, which precludes gathering data over the entire orbit."
The critical observations also happen during a low-downlink period for MESSENGER. "We can't fill up the spacecraft recorder with comet data because doing so could cause a backlog that impacts our primary mission of collecting observations from Mercury," he said.
But the team is optimistic that all will go as planned, he said. "We just need the comets to hold up their end of the bargain."
{...}
JHU APL - MESSENGER: MESSENGER's First Images of Comets Encke and ISON
Universe Today: Comets Encke and ISON Spotted from Mercury
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[ame="http://orbithangar.com/searchid.php?ID=6301"]Don't worry, it has already been done.[/ame]
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JHU APL:
MESSENGER Mission News
November 25, 2013
http://messenger.jhuapl.edu/
A Tale of Two Comets: MESSENGER Captures Images of Encke and ISON
On November 18, NASA's Mercury-orbiting MESSENGER spacecraft pointed its Mercury Dual Imaging System (MDIS) at 2P/Encke and captured this image of the comet as it sped within 2.3 million miles (3.7 million kilometers) of Mercury's surface. The next day, the probe captured this companion image of C/2012 S1 (ISON), as it cruised by Mercury at a distance of 22.5 million miles (36.2 million kilometers) on its way to its late-November closest approach to the Sun.
MESSENGER's cameras have been acquiring targeted observations of Encke since October 28 and ISON since October 26, although the first faint detections didn't come until early November. During the closest approach of each comet to Mercury, the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) and X-Ray Spectrometer (XRS) instruments also targeted the comets. Observations of ISON conclude on November 26, when the comet passes too close to the Sun, but MESSENGER will continue to monitor Encke with both the imagers and spectrometers through early December.
The spacecraft has a view of the comets very different from that of Earth-based observers. "MESSENGER imaged Encke only a few days before its perihelion when it was at its brightest," explains Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER's comet-observation campaign. "That we are so close to the comet at this time offers a chance to make important observations that could shed light on its asymmetric behavior about perihelion."
In contrast, ISON did not pass as close to Mercury, but the comet was between the Earth and Mercury when it passed closest to MESSENGER. "We saw the side opposite to that visible from Earth," says Vervack, "so our images and spectra are complementary to observations from Earth made at the same time and could aid in understanding the variable activity of the comet as it approached the Sun."
On the day that Encke was closest to Mercury, the MDIS wide-angle camera scanned the comet with all of its 12 filters while the instrument's narrow-angle camera (NAC) snapped images of the rotating comet every 10 minutes to capture a full 360-degree view. The imaging campaign for ISON was similar, with the NAC capturing a series of stills every 30 minutes.
Several ground- and space-based NASA observatories, as well as many other observatories around the world, are collecting data on the comets. However, none will be able to collect simultaneous images and spectra from X-ray through near-infrared wavelengths when the comets are so close to the Sun, as will MESSENGER. Vervack expects MESSENGER to gather 15 hours worth of data on Encke and another 25 hours on ISON. "These observations of Encke and ISON fill a gap in heliocentric coverage to which most other observatories don’t have access," Vervack says.
Scientists are still combing through the data collected by MASCS, but there are already confirmed detections of several molecules and atoms, including OH, NH, CS, oxygen, carbon, sulfur, and hydrogen. "Far-ultraviolet observations can't be made from ground-based observatories, and only a few instruments in space have been able to look at the comets in the ultraviolet," says Vervack. "The MASCS observations are therefore of great interest."
Scientists were also hoping to obtain the first definitive detections of cometary X-ray emission from silicon, magnesium, and aluminum. "NASA's Chandra X-ray space telescope has observed ISON and Encke and seen X-ray emission from them both," Vervack says. "We are able to make these observations when both comets are closer to the Sun, so the X-ray emissions have the potential to be much more intense." However, a series of large solar flares during the observations increased the contaminating background in the X-ray spectra and have complicated the analysis. "We can't help what the Sun does," says Vervack, "but we're going to analyze the data carefully to see if there are any detections to be had."
Taken together, the MESSENGER observations offer a varied science investigation of the comets. "Whereas the MDIS images will provide a global picture of the comet coma morphology, MASCS observations will inform us about the composition of the cometary ices and XRS may be able to tell us what the dust is made of," Vervack says.
"Comet encounters were not considered when the MESSENGER mission was designed," adds MESSENGER Principal Investigator Sean Solomon of Columbia University. "If Encke and ISON share a few of their secrets on the formation and evolution of the Solar System, the MESSENGER team will be delighted with the scientific bonus."
{...}
JHU APL:
MESSENGER Mission News
November 25, 2013
http://messenger.jhuapl.edu/
A Tale of Two Comets: MESSENGER Captures Images of Encke and ISON
On November 18, NASA's Mercury-orbiting MESSENGER spacecraft pointed its Mercury Dual Imaging System (MDIS) at 2P/Encke and captured this image of the comet as it sped within 2.3 million miles (3.7 million kilometers) of Mercury's surface. The next day, the probe captured this companion image of C/2012 S1 (ISON), as it cruised by Mercury at a distance of 22.5 million miles (36.2 million kilometers) on its way to its late-November closest approach to the Sun.
MESSENGER's cameras have been acquiring targeted observations of Encke since October 28 and ISON since October 26, although the first faint detections didn't come until early November. During the closest approach of each comet to Mercury, the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) and X-Ray Spectrometer (XRS) instruments also targeted the comets. Observations of ISON conclude on November 26, when the comet passes too close to the Sun, but MESSENGER will continue to monitor Encke with both the imagers and spectrometers through early December.
The spacecraft has a view of the comets very different from that of Earth-based observers. "MESSENGER imaged Encke only a few days before its perihelion when it was at its brightest," explains Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER's comet-observation campaign. "That we are so close to the comet at this time offers a chance to make important observations that could shed light on its asymmetric behavior about perihelion."
In contrast, ISON did not pass as close to Mercury, but the comet was between the Earth and Mercury when it passed closest to MESSENGER. "We saw the side opposite to that visible from Earth," says Vervack, "so our images and spectra are complementary to observations from Earth made at the same time and could aid in understanding the variable activity of the comet as it approached the Sun."
On the day that Encke was closest to Mercury, the MDIS wide-angle camera scanned the comet with all of its 12 filters while the instrument's narrow-angle camera (NAC) snapped images of the rotating comet every 10 minutes to capture a full 360-degree view. The imaging campaign for ISON was similar, with the NAC capturing a series of stills every 30 minutes.
Several ground- and space-based NASA observatories, as well as many other observatories around the world, are collecting data on the comets. However, none will be able to collect simultaneous images and spectra from X-ray through near-infrared wavelengths when the comets are so close to the Sun, as will MESSENGER. Vervack expects MESSENGER to gather 15 hours worth of data on Encke and another 25 hours on ISON. "These observations of Encke and ISON fill a gap in heliocentric coverage to which most other observatories don’t have access," Vervack says.
Scientists are still combing through the data collected by MASCS, but there are already confirmed detections of several molecules and atoms, including OH, NH, CS, oxygen, carbon, sulfur, and hydrogen. "Far-ultraviolet observations can't be made from ground-based observatories, and only a few instruments in space have been able to look at the comets in the ultraviolet," says Vervack. "The MASCS observations are therefore of great interest."
Scientists were also hoping to obtain the first definitive detections of cometary X-ray emission from silicon, magnesium, and aluminum. "NASA's Chandra X-ray space telescope has observed ISON and Encke and seen X-ray emission from them both," Vervack says. "We are able to make these observations when both comets are closer to the Sun, so the X-ray emissions have the potential to be much more intense." However, a series of large solar flares during the observations increased the contaminating background in the X-ray spectra and have complicated the analysis. "We can't help what the Sun does," says Vervack, "but we're going to analyze the data carefully to see if there are any detections to be had."
Taken together, the MESSENGER observations offer a varied science investigation of the comets. "Whereas the MDIS images will provide a global picture of the comet coma morphology, MASCS observations will inform us about the composition of the cometary ices and XRS may be able to tell us what the dust is made of," Vervack says.
"Comet encounters were not considered when the MESSENGER mission was designed," adds MESSENGER Principal Investigator Sean Solomon of Columbia University. "If Encke and ISON share a few of their secrets on the formation and evolution of the Solar System, the MESSENGER team will be delighted with the scientific bonus."
{...}
JHU APL:
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JHU APL:
MESSENGER Mission News
April 21, 2014
http://messenger.jhuapl.edu/
MESSENGER Completes Its 3,000th Orbit of Mercury, Sets Mark for Closest Approach
On April 20, MESSENGER completed its 3,000th orbit of Mercury and moved closer to the planet than any spacecraft has been before, dropping to an altitude of 199 kilometers (123.7 miles) above the planet's surface.
"We are cutting through Mercury's magnetic field in a different geometry, and that has shed new light on the energetic electron population," said MESSENGER Project Scientist Ralph McNutt, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "In addition, we are now spending more time closer to the planet in general -- and that has, in turn, increased the opportunities for all of the remote sensing instruments to make higher-resolution observations of the planet."
MESSENGER has been completing three orbits of Mercury every day since April 2012, when two orbit-correction maneuvers reduced its orbital period about Mercury from 12 hours to 8 hours. The shorter orbit has allowed the science team to explore new questions about Mercury's composition, geological evolution, and environment that were raised by discoveries made during the first year of orbital operations.
APL's Carolyn Ernst, the deputy instrument scientist for the Mercury Laser Altimeter (MLA), said the change from a 12- to an 8-hour orbit provided her team with 50% more altimetry tracks. "MLA coverage takes a long time to build up, and because of the small footprint of the laser, a lot of coverage is needed to obtain good spatial resolution. The more data we acquire, the better we resolve the topography of the planet," she said. "The 8-hour orbit has also allowed us to make more MLA reflectivity measurements, which have provided critical clues for characterizing Mercury's radar-bright deposits at high northern latitudes."
The probe has been edging closer and closer to Mercury since March 2013, at about the time that the spacecraft orbit's minimum altitude passed closest to Mercury's north pole.
APL's David Lawrence, a MESSENGER Participating Scientist, said he is excited about what the low-altitude orbits will reveal about Mercury's surface composition. "To date our compositional measurements with neutron, X-ray, and gamma-ray data have resolved only very large regions on Mercury's surface. Altitudes of less than 100 kilometers will enable us to pinpoint the compositional signatures of specific geologic features, which in turn will help us to understand how the surface formed and has changed over time."
MESSENGER's periapsis altitude will continue to decrease until the first orbit-correction maneuver of the low-altitude campaign, scheduled for June 17.
"The final year of MESSENGER's orbital operations will be an entirely new mission," added MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "With each orbit, our images, our surface compositional measurements, and our observations of the planet's magnetic and gravity fields will be higher in resolution than ever before. We will be able to characterize Mercury's near-surface particle environment for the first time. Mercury has stubbornly held on to many of its secrets, but many will at last be revealed."
MESSENGER Mission News
April 21, 2014
http://messenger.jhuapl.edu/
MESSENGER Completes Its 3,000th Orbit of Mercury, Sets Mark for Closest Approach
On April 20, MESSENGER completed its 3,000th orbit of Mercury and moved closer to the planet than any spacecraft has been before, dropping to an altitude of 199 kilometers (123.7 miles) above the planet's surface.
"We are cutting through Mercury's magnetic field in a different geometry, and that has shed new light on the energetic electron population," said MESSENGER Project Scientist Ralph McNutt, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "In addition, we are now spending more time closer to the planet in general -- and that has, in turn, increased the opportunities for all of the remote sensing instruments to make higher-resolution observations of the planet."
MESSENGER has been completing three orbits of Mercury every day since April 2012, when two orbit-correction maneuvers reduced its orbital period about Mercury from 12 hours to 8 hours. The shorter orbit has allowed the science team to explore new questions about Mercury's composition, geological evolution, and environment that were raised by discoveries made during the first year of orbital operations.
APL's Carolyn Ernst, the deputy instrument scientist for the Mercury Laser Altimeter (MLA), said the change from a 12- to an 8-hour orbit provided her team with 50% more altimetry tracks. "MLA coverage takes a long time to build up, and because of the small footprint of the laser, a lot of coverage is needed to obtain good spatial resolution. The more data we acquire, the better we resolve the topography of the planet," she said. "The 8-hour orbit has also allowed us to make more MLA reflectivity measurements, which have provided critical clues for characterizing Mercury's radar-bright deposits at high northern latitudes."
The probe has been edging closer and closer to Mercury since March 2013, at about the time that the spacecraft orbit's minimum altitude passed closest to Mercury's north pole.
APL's David Lawrence, a MESSENGER Participating Scientist, said he is excited about what the low-altitude orbits will reveal about Mercury's surface composition. "To date our compositional measurements with neutron, X-ray, and gamma-ray data have resolved only very large regions on Mercury's surface. Altitudes of less than 100 kilometers will enable us to pinpoint the compositional signatures of specific geologic features, which in turn will help us to understand how the surface formed and has changed over time."
MESSENGER's periapsis altitude will continue to decrease until the first orbit-correction maneuver of the low-altitude campaign, scheduled for June 17.
"The final year of MESSENGER's orbital operations will be an entirely new mission," added MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "With each orbit, our images, our surface compositional measurements, and our observations of the planet's magnetic and gravity fields will be higher in resolution than ever before. We will be able to characterize Mercury's near-surface particle environment for the first time. Mercury has stubbornly held on to many of its secrets, but many will at last be revealed."
Admiral_Ritt
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I wonder what the lowest altitude above Mercury this probe can sustain for
a 2 year extended mission. I recall the Moon allowed about 10-15 nm for
the Apollo Spacecraft. Maybe something in the range of 30-40nm would
be indicated.
Is the apparent motion of the surface too much for the imaging instruments,
if you get too close? And how close it that?
a 2 year extended mission. I recall the Moon allowed about 10-15 nm for
the Apollo Spacecraft. Maybe something in the range of 30-40nm would
be indicated.
Is the apparent motion of the surface too much for the imaging instruments,
if you get too close? And how close it that?
orb
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JHU APL:
MESSENGER Mission News
June 17, 2014
http://messenger.jhuapl.edu/
MESSENGER Modifies Orbit to Prepare for Low-Altitude Campaign
MESSENGER successfully completed the first orbit-correction maneuver of its Second Extended Mission this morning to raise its minimum altitude above Mercury from 113.9 kilometers (70.8 miles) to 155.1 kilometers (96.4 miles). This maneuver is the first of four designed to modify the spacecraft's orbit around Mercury so as to delay the spacecraft's inevitable impact onto Mercury's surface and allow scientists to continue to gather novel information about the innermost planet.
During the primary phase of the MESSENGER mission, the spacecraft's orbit around Mercury was highly eccentric, drifting between 200 and 500 kilometers (124 to 311 miles) above Mercury's surface at closest approach, and between 15,200 and 14,900 kilometers (9,445 to 9,258 miles) above the surface at its farthest point, and completing an orbit every 12 hours. Spacecraft operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, conducted several spacecraft maneuvers to counter the perturbing forces that caused MESSENGER's lowest orbital altitude to drift upward, away from its preferred observing geometry, and early in MESSENGER's First Extended Mission conducted a pair of maneuvers to reduce the orbital period to eight hours.
"In this final phase of the mission, the opposite effect is happening," explained the mission trajectory lead Jim McAdams of APL. "To extend the mission, we need to raise the minimum altitude by increasing the Mercury-relative speed of the spacecraft when it is farthest from Mercury."
For this latest orbit adjustment, MESSENGER was 82.9 million kilometers (51.5 million miles) from Earth and 69.8 million kilometers (43.3 million miles) from the Sun. The 3.2-minute-long maneuver -- which used two of the four largest monopropellant thrusters, with a small contribution from four of the 12 smallest monopropellant thrusters -- began at about 10:53 a.m., EDT. APL mission controllers verified the start of the maneuver 4.6 minutes later, when the first signals indicating spacecraft thruster activity reached MESSENGER's Mission Operations Center via NASA's Deep Space Network tracking station outside of Madrid, Spain.
"MESSENGER's results to date have revolutionized our knowledge of Mercury's global geology, the nature of volcanism across the surface, the cratering record, and the history of the planet's contraction, and they have also revealed unexpected discoveries, such as hollows," said APL's Nancy Chabot, who chairs MESSENGER's Geology Discipline Group. During the remainder of MESSENGER's mission, the focus of geological observations will narrow from a global perspective to views of selected areas in unprecedented detail, she explained.
"With the low-altitude imaging campaign, MESSENGER will acquire the highest-resolution images ever obtained of Mercury, enabling us to search for volcanic flow fronts, small-scale tectonic features, layering in crater walls, locations of impact melt, and new aspects of hollows. Those detailed views will provide a new understanding of Mercury's geological evolution," she said.
The measurement resolution of Mercury's gravity and internal magnetic fields improves markedly as the altitude of the MESSENGER spacecraft decreases. "This improvement means that smaller-scale and weaker-amplitude features can be mapped, and in the case of magnetic measurements, the external and internal fields can be separated with greater fidelity," said Roger Phillips of the Southwest Research Institute in Boulder, Colorado.
"MESSENGER will continue its downward march, interrupted by the final three orbit-correction maneuvers, but also achieving altitudes lower than 50 kilometers for the first time," said Phillips, who chairs MESSENGER's Geophysics Discipline Group. "For the magnetic field, the question of whether the crust has retained an ancient, frozen-in (remanent) magnetic field, as have Mars and Earth, can be answered, and a higher-resolution picture of the field generated by Mercury's liquid outer core can be obtained. For the gravity field, the signatures of large fold-and-thrust belts and of impact craters will shed light on the structure of the crust and the early history of Mercury."
MESSENGER's geochemical measurements obtained during the upcoming months will provide measurements with vastly improved spatial resolution, according to APL's Patrick Peplowski, the instrument scientist for the Gamma-Ray and Neutron Spectrometer. "Not only will the low-altitude campaign help our overall efforts to map Mercury's surface composition with the best possible spatial resolution, we will now be able to obtain spatially resolved measurements of features that were previously too small to resolve with the geochemical instruments," he said. "For example, we have opportunities to study the chemical composition of pyroclastic deposits and the mysterious low-reflectance material. We are also hoping to spatially resolve individual ice-hosting craters for the first time."
Even with today's maneuver, the spacecraft's altitude at closest approach will continue to decrease until raised by additional maneuvers in September and October of this year and January 2015. At that point, MESSENGER will have spent its accessible propellant, and additional altitude-changing maneuvers will not be possible. In March 2015, the spacecraft will impact the surface of Mercury, having successfully completed four years in orbit about Mercury.
MESSENGER Mission News
June 17, 2014
http://messenger.jhuapl.edu/
MESSENGER Modifies Orbit to Prepare for Low-Altitude Campaign
MESSENGER successfully completed the first orbit-correction maneuver of its Second Extended Mission this morning to raise its minimum altitude above Mercury from 113.9 kilometers (70.8 miles) to 155.1 kilometers (96.4 miles). This maneuver is the first of four designed to modify the spacecraft's orbit around Mercury so as to delay the spacecraft's inevitable impact onto Mercury's surface and allow scientists to continue to gather novel information about the innermost planet.
During the primary phase of the MESSENGER mission, the spacecraft's orbit around Mercury was highly eccentric, drifting between 200 and 500 kilometers (124 to 311 miles) above Mercury's surface at closest approach, and between 15,200 and 14,900 kilometers (9,445 to 9,258 miles) above the surface at its farthest point, and completing an orbit every 12 hours. Spacecraft operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, conducted several spacecraft maneuvers to counter the perturbing forces that caused MESSENGER's lowest orbital altitude to drift upward, away from its preferred observing geometry, and early in MESSENGER's First Extended Mission conducted a pair of maneuvers to reduce the orbital period to eight hours.
"In this final phase of the mission, the opposite effect is happening," explained the mission trajectory lead Jim McAdams of APL. "To extend the mission, we need to raise the minimum altitude by increasing the Mercury-relative speed of the spacecraft when it is farthest from Mercury."
For this latest orbit adjustment, MESSENGER was 82.9 million kilometers (51.5 million miles) from Earth and 69.8 million kilometers (43.3 million miles) from the Sun. The 3.2-minute-long maneuver -- which used two of the four largest monopropellant thrusters, with a small contribution from four of the 12 smallest monopropellant thrusters -- began at about 10:53 a.m., EDT. APL mission controllers verified the start of the maneuver 4.6 minutes later, when the first signals indicating spacecraft thruster activity reached MESSENGER's Mission Operations Center via NASA's Deep Space Network tracking station outside of Madrid, Spain.
"MESSENGER's results to date have revolutionized our knowledge of Mercury's global geology, the nature of volcanism across the surface, the cratering record, and the history of the planet's contraction, and they have also revealed unexpected discoveries, such as hollows," said APL's Nancy Chabot, who chairs MESSENGER's Geology Discipline Group. During the remainder of MESSENGER's mission, the focus of geological observations will narrow from a global perspective to views of selected areas in unprecedented detail, she explained.
"With the low-altitude imaging campaign, MESSENGER will acquire the highest-resolution images ever obtained of Mercury, enabling us to search for volcanic flow fronts, small-scale tectonic features, layering in crater walls, locations of impact melt, and new aspects of hollows. Those detailed views will provide a new understanding of Mercury's geological evolution," she said.
The measurement resolution of Mercury's gravity and internal magnetic fields improves markedly as the altitude of the MESSENGER spacecraft decreases. "This improvement means that smaller-scale and weaker-amplitude features can be mapped, and in the case of magnetic measurements, the external and internal fields can be separated with greater fidelity," said Roger Phillips of the Southwest Research Institute in Boulder, Colorado.
"MESSENGER will continue its downward march, interrupted by the final three orbit-correction maneuvers, but also achieving altitudes lower than 50 kilometers for the first time," said Phillips, who chairs MESSENGER's Geophysics Discipline Group. "For the magnetic field, the question of whether the crust has retained an ancient, frozen-in (remanent) magnetic field, as have Mars and Earth, can be answered, and a higher-resolution picture of the field generated by Mercury's liquid outer core can be obtained. For the gravity field, the signatures of large fold-and-thrust belts and of impact craters will shed light on the structure of the crust and the early history of Mercury."
MESSENGER's geochemical measurements obtained during the upcoming months will provide measurements with vastly improved spatial resolution, according to APL's Patrick Peplowski, the instrument scientist for the Gamma-Ray and Neutron Spectrometer. "Not only will the low-altitude campaign help our overall efforts to map Mercury's surface composition with the best possible spatial resolution, we will now be able to obtain spatially resolved measurements of features that were previously too small to resolve with the geochemical instruments," he said. "For example, we have opportunities to study the chemical composition of pyroclastic deposits and the mysterious low-reflectance material. We are also hoping to spatially resolve individual ice-hosting craters for the first time."
Even with today's maneuver, the spacecraft's altitude at closest approach will continue to decrease until raised by additional maneuvers in September and October of this year and January 2015. At that point, MESSENGER will have spent its accessible propellant, and additional altitude-changing maneuvers will not be possible. In March 2015, the spacecraft will impact the surface of Mercury, having successfully completed four years in orbit about Mercury.
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NASA: "NASA's MESSENGER Spots Giant Space Weather Effects at Mercury"
The gray line shows the standing bow shock in front of Mercury. The signature of material flowing in a vastly different direction than the solar wind -- an HFA -- can be seen in red at the upper right.
Image Credit: NASA/Duberstein
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JHU APL:
MESSENGER Mission News
July 28, 2014
http://messenger.jhuapl.edu/
MESSENGER Gets Closer to Mercury than Ever Before
On July 25, MESSENGER moved closer to Mercury than any spacecraft has before, dropping to an altitude at closest approach of only 100 kilometers (62 miles) above the planet's surface.
"The science team is implementing a remarkable campaign that takes full advantage of MESSENGER's orbital geometry, and the spacecraft continues to execute its command sequences flawlessly as the 14th Mercury year of the orbit phase comes to a close," said MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory (APL).
The latest observational campaign includes closer looks at polar ice deposits, unusual geological features, and the planet's gravity and magnetic fields "in ways that have never been possible," said APL's Ralph McNutt, MESSENGER's Project Scientist. "This dip in altitude is allowing us to see Mercury up close and personal for the first time."
Because of progressive changes to the orbit over time, MESSENGER's minimum altitude will continue to decrease. On August 19, the minimum altitude will be cut in half, to 50 kilometers. Closest approach will be halved again to 25 kilometers on September 12, noted MESSENGER Mission Design Lead Engineer Jim McAdams, also of APL.
"Soon after reaching 25 kilometers above Mercury, an orbit-correction maneuver (OCM-10) will raise this minimum altitude to about 94 kilometers," he said. "Two more maneuvers, on October 24 and January 21, 2015, will raise the minimum altitude sufficiently to delay the inevitable -- impact onto Mercury's surface -- until March 2015."
MESSENGER Mission News
July 28, 2014
http://messenger.jhuapl.edu/
MESSENGER Gets Closer to Mercury than Ever Before
On July 25, MESSENGER moved closer to Mercury than any spacecraft has before, dropping to an altitude at closest approach of only 100 kilometers (62 miles) above the planet's surface.
"The science team is implementing a remarkable campaign that takes full advantage of MESSENGER's orbital geometry, and the spacecraft continues to execute its command sequences flawlessly as the 14th Mercury year of the orbit phase comes to a close," said MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory (APL).
The latest observational campaign includes closer looks at polar ice deposits, unusual geological features, and the planet's gravity and magnetic fields "in ways that have never been possible," said APL's Ralph McNutt, MESSENGER's Project Scientist. "This dip in altitude is allowing us to see Mercury up close and personal for the first time."
Because of progressive changes to the orbit over time, MESSENGER's minimum altitude will continue to decrease. On August 19, the minimum altitude will be cut in half, to 50 kilometers. Closest approach will be halved again to 25 kilometers on September 12, noted MESSENGER Mission Design Lead Engineer Jim McAdams, also of APL.
"Soon after reaching 25 kilometers above Mercury, an orbit-correction maneuver (OCM-10) will raise this minimum altitude to about 94 kilometers," he said. "Two more maneuvers, on October 24 and January 21, 2015, will raise the minimum altitude sufficiently to delay the inevitable -- impact onto Mercury's surface -- until March 2015."
MaverickSawyer
Acolyte of the Probe
Wow... is it really that close to the end of the mission? 
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MESSENGER has been in orbit since 2011 and for far longer than planned. BepiColombo will follow MESSENGER soon, although it looks like BepiColombo's launch has been delayed a year until 2016, making it enter orbit around Mercury two years later in 2024. Nonetheless, Mercury is finally being properly explored. Russia has plans to launch a Mercury lander in the late 2020s following their lunar landers, however likely that may be. Now Venus feels lonely.Wow... is it really that close to the end of the mission?
MaverickSawyer
Acolyte of the Probe
And Neptune and Uranus. They've only been visited once each.
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Active member
Rosetta isn't the only spacecraft in the solar system right now. MESSENGER has also taken a stunning set of photographs recently as the spacecraft descends towards Mercury.
The Planetary Society: "Buzz Mercury's North Polar Region in This New MESSENGER Video"
A graph of MESSENGER's projected altitude:
A 10-year anniversary graphic (like Cassini), click to enlarge:
The Planetary Society: "Buzz Mercury's North Polar Region in This New MESSENGER Video"
A graph of MESSENGER's projected altitude:
A 10-year anniversary graphic (like Cassini), click to enlarge:
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MESSENGER's View of This Week's Lunar Eclipse.
http://messenger.jhuapl.edu/news_room/details.php?id=265
http://messenger.jhuapl.edu/news_room/details.php?id=265
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JHU APL:
MESSENGER Mission News
October 15, 2014
http://messenger.jhuapl.edu/
MESSENGER Provides First Optical Images of Ice Near Mercury's North Pole
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has provided the first optical images of ice and other frozen volatile materials within permanently shadowed craters near Mercury's north pole. The images not only reveal the morphology of the frozen volatiles, but they also provide insight into when the ices were trapped and how they've evolved, according to an article published today in the journal, Geology.
Two decades ago, Earth-based radar images of Mercury revealed the polar deposits, postulated to consist of water ice. That hypothesis was later confirmed by MESSENGER through a combination of neutron spectrometry, thermal modeling, and infrared reflectometry. "But along with confirming the earlier idea, there is a lot new to be learned by seeing the deposits," said lead author Nancy Chabot, the Instrument Scientist for MESSENGER's Mercury Dual Imaging System (MDIS) and a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
Beginning with MESSENGER's first extended mission in 2012, scientists launched an imaging campaign with the broadband clear filter of MDIS's wide-angle camera (WAC). Although the polar deposits are in permanent shadow, through many refinements in the imaging, the WAC was able to obtain images of the surfaces of the deposits by leveraging very low levels of light scattered from illuminated crater walls. "It worked in spectacular fashion," said Chabot.
The team zeroed in on Prokofiev, the largest crater in Mercury's north polar region found to host radar-bright material. "Those images show extensive regions with distinctive reflectance properties," Chabot said. "A location interpreted as hosting widespread surface water ice exhibits a cratered texture indicating that the ice was emplaced more recently than any of the underlying craters."
In other areas, water ice is present, she said, "but it is covered by a thin layer of dark material inferred to consist of frozen organic-rich compounds." In the images of those areas, the dark deposits display sharp boundaries. "This result was a little surprising, because sharp boundaries indicate that the volatile deposits at Mercury's poles are geologically young, relative to the time scale for lateral mixing by impacts," said Chabot.
"One of the big questions we've been grappling with is 'When did Mercury's water ice deposits show up?' Are they billions of years old, or were they emplaced only recently?" Chabot said. "Understanding the age of these deposits has implications for understanding the delivery of water to all the terrestrial planets, including Earth."
Overall, the images indicate that Mercury's polar deposits either were delivered to the planet recently or are regularly restored at the surface through an ongoing process.
The images also reveal a noteworthy distinction between the Moon and Mercury, one that may shed additional light on the age of the frozen deposits. "The polar regions of Mercury show extensive areas that host water ice, but the Moon's polar regions -- which also have areas of permanent shadows and are actually colder -- look different," Chabot said.
"One explanation for differences between the Moon and Mercury could be that the volatile polar deposits on Mercury were recently emplaced," according to the paper. "If Mercury's currently substantial polar volatile inventory is the product of the most recent portion of a longer process, then a considerable mass of volatiles may have been delivered to the inner Solar System throughout its history."
"That's a key question," Chabot said. "Because if you can understand why one body looks one way and another looks different, you gain insight into the process that's behind it, which in turn is tied to the age and distribution of water ice in the Solar System. This will be a very interesting line of inquiry going forward."
{...}
MESSENGER Mission News
October 15, 2014
http://messenger.jhuapl.edu/
MESSENGER Provides First Optical Images of Ice Near Mercury's North Pole
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has provided the first optical images of ice and other frozen volatile materials within permanently shadowed craters near Mercury's north pole. The images not only reveal the morphology of the frozen volatiles, but they also provide insight into when the ices were trapped and how they've evolved, according to an article published today in the journal, Geology.
Two decades ago, Earth-based radar images of Mercury revealed the polar deposits, postulated to consist of water ice. That hypothesis was later confirmed by MESSENGER through a combination of neutron spectrometry, thermal modeling, and infrared reflectometry. "But along with confirming the earlier idea, there is a lot new to be learned by seeing the deposits," said lead author Nancy Chabot, the Instrument Scientist for MESSENGER's Mercury Dual Imaging System (MDIS) and a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
Beginning with MESSENGER's first extended mission in 2012, scientists launched an imaging campaign with the broadband clear filter of MDIS's wide-angle camera (WAC). Although the polar deposits are in permanent shadow, through many refinements in the imaging, the WAC was able to obtain images of the surfaces of the deposits by leveraging very low levels of light scattered from illuminated crater walls. "It worked in spectacular fashion," said Chabot.
The team zeroed in on Prokofiev, the largest crater in Mercury's north polar region found to host radar-bright material. "Those images show extensive regions with distinctive reflectance properties," Chabot said. "A location interpreted as hosting widespread surface water ice exhibits a cratered texture indicating that the ice was emplaced more recently than any of the underlying craters."
In other areas, water ice is present, she said, "but it is covered by a thin layer of dark material inferred to consist of frozen organic-rich compounds." In the images of those areas, the dark deposits display sharp boundaries. "This result was a little surprising, because sharp boundaries indicate that the volatile deposits at Mercury's poles are geologically young, relative to the time scale for lateral mixing by impacts," said Chabot.
"One of the big questions we've been grappling with is 'When did Mercury's water ice deposits show up?' Are they billions of years old, or were they emplaced only recently?" Chabot said. "Understanding the age of these deposits has implications for understanding the delivery of water to all the terrestrial planets, including Earth."
Overall, the images indicate that Mercury's polar deposits either were delivered to the planet recently or are regularly restored at the surface through an ongoing process.
The images also reveal a noteworthy distinction between the Moon and Mercury, one that may shed additional light on the age of the frozen deposits. "The polar regions of Mercury show extensive areas that host water ice, but the Moon's polar regions -- which also have areas of permanent shadows and are actually colder -- look different," Chabot said.
"One explanation for differences between the Moon and Mercury could be that the volatile polar deposits on Mercury were recently emplaced," according to the paper. "If Mercury's currently substantial polar volatile inventory is the product of the most recent portion of a longer process, then a considerable mass of volatiles may have been delivered to the inner Solar System throughout its history."
"That's a key question," Chabot said. "Because if you can understand why one body looks one way and another looks different, you gain insight into the process that's behind it, which in turn is tied to the age and distribution of water ice in the Solar System. This will be a very interesting line of inquiry going forward."
{...}
TMac3000
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It looks so much like the Moon...
EDIT: :ninja:'d by sorindafabico
EDIT: :ninja:'d by sorindafabico
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